Napster will launch a new mobile music service today that allows users to download as many songs as they like, so long as they keep paying a subscription.

Napster to Go will make available the company's collection of one million songs, but will use Microsoft's newly developed Janus copy protection technology to time stamp the tracks.

Every time the music player is connected to the computer the songs are checked against the user's subscription, and will not play unless the user has paid their monthly dues.

Napster to Go customers will pay £14.95 per month for unlimited downloads, but must pay 79p per track or £7.95 per album if they burn the tracks to CD.

The strategy puts Napster head to head with Apple's iTunes service, where users must buy each track. However, the Napster service will work on a variety of music players whereas Apple users must use an iPod.

"Napster To Go will change the music industry forever," said Chris Gorog, Napster chairman and chief executive.

"Our dream has been to offer music fans the key to the world's music library for a low monthly cost, and by extending online access to those on the move we have put in place the final piece of the jigsaw.

"The biggest brand in digital music has once again underlined its pedigree as an industry pioneer, and we are extremely proud that Napster is first to market with this revolutionary new way to enjoy music."

Napster has earmarked $30m to advertise the new service, including slots on this Sunday's Superbowl, traditionally the most expensive advertising event of the year.

The 'Do the Math' theme of the ads points out that consumers could pay $15 a month to get 10,000 songs from Napster or $10,000 to get 10,000 songs from iTunes.